(1) Field of the Invention
The present invention relates to a laminated abutment, a rotor provided with such an abutment, and an aircraft. More particularly, the invention relates to a rotary-wing aircraft and to a rotor of its rotary wing.
A rotary-wing aircraft generally includes at least one rotor for providing lift and possibly propulsion. The lift rotor includes a hub carrying a plurality of blades.
(2) Description of Related Art
The rotor may thus include one laminated abutment per blade for hinging each blade to the hub about a flapping axis, a lead-lag axis, and a pitch-variation axis. Thus, each laminated abutment holds a blade on the hub of a rotorcraft rotor in hinged manner.
Document FR 2 497 173 describes a laminated abutment comprising a stack of alternating layers of flexible material and of a rigid material.
Document FR 2 497 173 seeks to limit the fatigue wear of an abutment by providing layers of flexible material in the shape of spherical caps having thicknesses that increase radially and progressively along an axis of symmetry going from an inner strength member to an outer strength member.
In addition, a rotor of a rotary-wing aircraft may include a device for avoiding the phenomena of ground resonance and of air resonance.
Such a device conventionally includes a lead-lag damper connecting each blade to the hub or to an adjacent blade, the damper bringing stiffness and damping to the drag vibration mode of the rotor. Such a damper is sometimes referred to as a “frequency adapter”.
Document U.S. Pat. No. 5,449,152 describes tubular lead-lag dampers. In particular, document U.S. Pat. No. 5,449,152 discloses a lead-lag damper provided with layers of elastomers having different characteristics.
Document U.S. Pat. No. 4,886,419 proposes a laminated abutment for firstly hinging a blade to a hub, and secondly damping the lead-lag movements of the blade.
That abutment thus includes an inner strength member and an outer strength member, a stack of flexible main layers and of rigid secondary layers being arranged between the inner strength member and the outer strength member.
In that abutment, each main layer comprises two different materials.
Document U.S. Pat. No. 5,913,659 describes a device provided with a flat elastomeric damper and with a spherical elastomeric damper.
The following documents are also known: GB 660 560, US 2003/0235499, WO 2010/068209, EP 0 187 265, and U.S. Pat. No. 2,958,526. Document GB 660 560 describes a device for connecting together two members. In an embodiment, the device comprises three concentric tubes representing a central tube, an intermediate tube, and an outer tube.
A first layer of rubber is arranged between the central tube and the intermediate tube, and a second layer of rubber is arranged between the intermediate tube and the outer tube.
The first layer includes two sectors that are bonded to the central tube and to the intermediate tube, the sectors being connected together by circumferential portions that are bonded to the central tube.
In addition, the second layer includes two sectors that are bonded to the outer tube and to the intermediate tube, the sectors being connected together by circumferential portions that are bonded to the intermediate tube.
Thus, document GB 660 560 does not present a laminated abutment firstly for holding a blade on a hub and hinging it thereto, and secondly for adapting the drag vibration mode of a rotor.